The MIMO (multiple input multiple output) technology is one of important contents in LTE-A standardization, in which adaptive adjustment in a direction of a beam can be achieved by using multiple antennas, thereby achieving a goal of increasing user signal to interference plus noise ratio or interference coordination. A main gain of the MIMO is originated from grasp of channel state information (CSI) by a base station side, channel information being obtained by CSI feedback of the user, and the CSI feedback being based on a predefined codebook.
As the continuous increase of demands for data rates, a future MIMO technology shall be developed in a direction of full-space 3D beamforming/precoding. The 3D MIMO precoding enables a beam to be adjusted in a vertical dimension, which increases a resolution of the beam, and is able to align the user or avoid interference more efficiently.
However, it was found by the inventors that in an existing solution, increase of overhead of CSI feedback and reference signal brought by the 3D MIMO system often becomes a bottleneck of its performance increase, if it is not optimally designed, the performance of 3D MIMO precoding will be greatly constrained.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.